Benzoic acid derivatives

ABSTRACT

The invention relates to a series of new compounds, to salts of these compounds and to methods for the preparation of the compounds. The new compounds have the general formula:   IN WHICH R1 is selected from the group consisting of alkyl radicals with from 3 to 8 carbon atoms in the carbon chain; mononuclear aromatically and mono-nuclear heterocyclically substituted methyl and ethyl; A is selected from the group consisting of unsubstituted and substituted phenoxy radicals, phenylthio radicals, benzoyl, benzyl and Alpha -hydroxybenzyl radicals; R2 is selected from the group consisting of hydrogen, lower alkyl groups, lower alkoxy groups, unsubstituted and monoand di-substituted amine groups. In particular the compounds of formula (I) have a pronounced diuretic and/or saluretic activity which is surprising in view of the chemical structure and the absence of a sulphamyl group.

United States Patent [1 1 Feit et al. Sept. 2, 1975 BENZOIC ACID DERIVATIVES [75] Inventors: Peter Werner Feit, Gentofte; Ole [57] ABSTRACT Bent Tvaermose Nielsen, both of The invention relates to a series of new compounds, to Vanlose, Denmark salts of these compounds and to methods for the prep- 73 Assignee: Lovens Kemiske Fabrik igz ggg g f fig The new cmpunds have Produktionsaktieselskab, Ballerup, g Denmark 3 22 Filed: Oct. 25, 1973 2 21 Appl. No.: 409,393 1 Related U.S. ApplicationData R -C-HN 6 GOOH [62] Division of Ser. No. 149,012, June l, 1971, Pat. No.

in which R is selected from the group consisting of [52] US. Cl 260/516; 260/479 R; 260/50l.l; alkyl radicals with from 3 to 8 carbon atoms in the 260/50l.l7; 2 60/517; 260/479 S carbon chain; mono-nuclear aromatically and mono- [51] Int. Cl. C07C 149/42 nuclear heterocyclically substituted methyl and ethyl; [58] Field of Search 260/470, 516 A is selected from the group consisting of unsubstituted and substituted phenoxy radicals, phenylthio [56] References Cited radicals, benzoyl, benzyl and a-hydroxybenzyl radin- STATES PATENTS cals; R is selected from the group consisting of hydro- 3,493,5s4 2/1970 Weinstock et al, 260/470 f alkyl groups P F f unsub' 3,577,409 5/1971 Cragoe 424 229 St'mted and and dl'substltuted amme groups- 3,634,583 l/l972 Feit 260/519 In particular the compounds of f rmula (I) have 3 3,806,542 4/1974 Werner 260/470 pronounced di i d/ saluretic i i hi i Primary Examiner-John F. Terapane Attorney, Agent, or Firm-Jackson, Jackson &

Chovanes surprising in view of the chemical structure and the absence of a sulphamyl group.

2 Claims, No Drawings BENZOIC ACID DERIVATIVES This is a division of Ser. No. 149,012, filed June 1, 1971, now U.S. Pat. No. 3,819,692.

This invention relates to a series of new compounds, to salts of these compounds and to methods for the preparation of the compounds. The new compounds have the general formula:

COOH

in which R is selected from the group consisting of alkyl radicals with from 3 to 8 carbon atoms in the carbon chain; mono-nuclear aromatically and mononuclear heterocyclically substituted methyl and ethyl; A is selected from the group consisting of unsubstituted and substituted phenoxy radicals, phenylthio radicals, benzoyl, benzylanda-hydroxybenzyl radicals; R is selected from the group consisting of hydrogen, lower alkyl groups, lower alkoxy groups, unsubstituted and mono-lower and di-lower alkylamino groups.

Whenever the expression lower alkyl is used in the foregoing and in the following it stands for a straight or branched alkyl radical with from l-6 carbon atoms in the chain.

In particular, R can be a straight or branched alkyl radical, e.g., a propyl, isopropyl, butyl, isobutyl, or tert. butyl radical, or one of the different isomeric pentyl, hexyl, heptyl or octyl radicals. When R represents a mono-nuclear heterocyclically substituted methyl or ethyl group the heterocycle can be a monocyclic radical containing one oxygen, sulphur or nitrogen atom as ring member, e.g. 2-, 3- or 4-pyridyl, 2- or 3-furyl or -thienyl. Illustrative examples of such mono-nuclear substituted methyl and ethyl groups are benzyl, lor 2-phenylethyl, furyl-methyl and the corresponding ethyl radicals.

The benzene nucleus of the substituents A and R, of formula (1) can be substituted in different positions with different groups, such as one or more halogen atoms, e.g., chlorine or bromine atoms, lower alkyl,

halo-lower alkyl, e.g., trifluoromethyl, chloromethyl,

such as methylthio, ethylthio, isopropylthio, butylthio or isobutylthio.

In the formula (1) R preferably stands for alkyl with from l'5 carbon atoms in the chain which can be straight or branched, or for alkoxy groups with from l-4 carbon atoms in the chain which can be straight or branched, or for amino, mono-lower alkylamino or dilower alkylamino groups, e.g., methylamino,

ethylamino, diisopropylamino and similar primary and secondary amines with from 14 carbon atoms in the alkyl group attached to the amino group.

The salts of the compounds are in particular pharmaceutically acceptable salts, and include, for example, alkali metal salts, alkaline earth metal salts, the ammonium salt, or amine salts formed, for instance, from mono-, di-, or trialkylamines, or mono-, di-, or trialkanolamines or cyclic amines.

According to animal experiments performed it has now been found that the compounds of formula I of the invention have a pronounced diuretic and/or saluretic activity which is surprising in view of the chemical structure and the absence of a sulphamyl group. The low toxicity in connection with a favourable therapeutic index make the present compounds particularly valuable.

For use in human and veterinary practice the compounds can be administered by the oral, enteral or parenteral route, and can preferably be prescribed in the form of e.g., tablets containing the free acid, or a salt thereof with an atoxic base mixed with carriers and/or auxiliary agents.

According to preliminary trials the compounds of the invention are appropriately given by the oral route in doses from 5 mg. to 50 mg. each, once, twice, or thrice daily always depending on the condition of the patient and under direction of the physician. When given by the parenteral route the doses are preferably 2.5 mg. to 25 mg. administered appropriately once a day. Salts, which are soluble in water, are with advantage used in preparations for injection.

The pharmaceutical preparations are useful in the treatment of oedematous conditions e.g. cardiac, hepatic, renal, lung and brain oedema, or oedematous conditions during pregnancy, and of pathological conditions which produce an abnormal retension of the electrolytes of the body and in the treatment of hypertension.

In the method according to the invention the new, highly active compounds of formula I can be prepared from an inactive or very weak starting material of the general formula:

NH-R

HZN COOH in which A and R are as defined above.

This compound can be transformed into a compound of the invention by acylation with an acid of the formula R COOH in which R has the meaning as defined hereinbefore or a reactive derivative of the acid in question, e.g., an anhydride, a mixed anhydride, or an acid halide, preferably an acid chloride of a carboxylic acid such as acetic acid, or with a carbamyl halide such as dimethylcarbamyl chloride, or by reacting with an alkylisocyanate or isocyanic acid, or an alkyl chlorocarbonate to form the compound of formula 1. These reactions are all well-known to the man skilled in the an.

Depending on the reaction conditions the comthereof was esters thereof. In the latter case the ester obtained is subsequently saponified.

The starting materials of formula II in which the Nl-l-R group is placed in the 3-position can be prepared in several ways. In one method 3-amino-4-A-5- nitrobenzoic acids are alkylated at the 3-amino group followed by a reduction of the S-nitro group to a amino group. The alkylation processes are well known methods which are described in the complete specification of our South African Pat. No. 69/8615. The reduction of the nitro group can be performed for instance by a catalytic hydrogenation or by reduction with e.g. dithionite or ferro salts in suitable solvents depending of what A stands for. The 3-amino-4-A-5-nitro-benzoic acids are new compounds, which can be prepared from the corresponding 4-A-3,5-dinitro-benzoic acids by a partial reduction for instance by addition of sodium dithionite to the pyridium salt of the acid in question at or about room temperature.

The compounds 4-A-3,5 -dinitro-benzoic acids are partly known compounds and the unknown can be prepared by methods described in the chemical literature for similar compounds. For example are the 4-benzoylderivatives prepared according to the following reaction:

in which reaction the starting substance of formula lll is known and has been described in Chem. Ber. 26, p. 2983, (1893).

The products of formula II in which A is benzyl can be prepared from the corresponding benzoylderivatives by a Wolff-Kishner reaction as a last step.

The compounds of formula (l) in which A is an ahydroxybenzylradical can be prepared from the corresponding benzoyl-derivatives by reduction, preferably with sodium borohydride.

When A is phenoxy or phenylthio the compounds can be prepared from a 4-halo-3,5-dinitro benzoic acid by reacting this compound with a compound of the formula A-H, i.e., with a phenol or a thiophenol, preferably at a pH above 7.

The starting materials of formula II in which the Nl-l-R, group is placed in the 2-position and A represents phenoxy or phenylthio can for instance be prepared from 2-NH-R -4-A-5-nitro-benzoic acids by reduction of the nitro group by known methods. As already mentioned above the reduction method preferred depends on the meaning of the substituent A. The 2-Nl-l-R -4-A-5-nitro-benzoic acids can be prepared e.g., from 2-fluoro-4-chloro-benzoic acid which by nitration is converted to the 2-fluoro-4-chloro-5- nitro-benzoic acid, whereupon the fluoro atom is replaced by the Nl-l-R group and finally the chloro atom in the 4-position is replaced by the group A by reaction with a compound of the formula AH, i.e., with a phenol, a thiophenol preferably at a pH above seven.

The starting materials of formula II in which the Nl-l-R group is placed in the 2-position and A is benzoyl can be prepared from the known 2-amino-4- carboxy-S-nitro-toluene which after acylation of the amino group is subjected to a Friedel-Crafts reaction whereby the carboxy group is converted into a 4- benzoyl group. By oxydation in known manner the methyl group is oxydized to a carboxy group and after deacylation of the protected amino group the 2-amino-4-benzoyl-S-nitro benzoic acid is obtained. By alkylation of the Z-amino group followed by a reduction of the S-nitro group by well-known processes the compounds of formula II in which A is a benzoyl radical is obtained. These compounds can be converted to compounds of formula ll in which A is a-hydroxybenzyl by a reduction with for instance sodium borohydride and to the compounds of formula ll in which A is benzyl by a Wolff-Kishner reduction.

The preparation of the compounds are described more in detail in the following Examples which are only illustrative and not limiting for the invention:

EXAMPLE 1.

A. 3-Amino-5-nitro-4-phenoxy-benzoic acid To a suspension of 3,5-dinitro-4phenoxy-benzoic acid g.) in water (400 ml.) pyridine (60 ml.) is added, while stirring. When the formation of the pyridine salt is completed the mixture is cooled to 10 C. and a solution of sodium dithionite (52 g. containing COOC H 87% sodium dithionite) in water (400 ml.) is added during 10 minutes, while stirring and keeping the temperature below 12 C. Then the still cold solution is filtered, and the filtrate acidified by addition of 4 N hydrochloric acid (220 ml. After stirring for 8 hours, the precipitated 3-amino-5-nitro-4-phenoxy-benzoic acid is collected by filtration and recrystallized from ethanol/water. The compound is obtained with a melting point of 231232 C.

B. Ethyl -3-benzylamino-5-nitro-4-phenoxy-benzoate A mixture of 3-amino-5-nitro-4-phenoxy-benzoic acid (27.4 g. benzyl bromide (43 g.) and ethanol (400 ml.) is refluxed for 4 hours. An additional amount of benzyl bromide (24 g.) is added and the refluxing is continued for 4 hours. After cooling the precipitated ethyl 3-benzylamino-5-nitro-4-phenoxy-benzoate is collected by filtration. After recrystallization from ethanol, the ester is obtained with a melting point of 101 102 C.

C. 3-Benzylamino-5-nitro-4-phenoxy-benzoic acid A mixture of ethyl 3-benzylamino-5-nitro-4- phenoxy-benzoate (15 g.), ethanol (225 ml.) and l N sodium hydroxide (225 ml.) is heated on a steam bath for 30 minutes. 4 N hydrochloric acid (60 ml.) is added and, after cooling, the precipitated 3-benzylamin0-5- nitro-4-phenoxy-benzoic acid is collected by filtration. After recrystallization from ethanol .the acid is obtained with a melting point of 190 192 C.

D. 5-Amino-3-benzylamino-4-phenoxy-benzoic acid To a solution of sodium dithionite (26 g. containing 87% of sodium dithionite) in water (160 ml.) aqueous ammonia ml. containing 25% of ammonia) and 3- benzylamino-5-nitro-4-phenoxy-benzoic acid 13 g.) are added, while stirring. After 15 minutes the reaction mixture is heated on a steam bath for 30 minutes. 2 N hydrochloric acid (320 ml.) is added and the heating is continued for minutes. After cooling, the precipitated 5-amino-3-benzylamino-4-phenoxy-benzoic acid is collected by filtration, washed with water and recrystallized from ethanol. The compound is obtained with a melting point of 184 185 C.

EXAMPLE 2.

A. 3,S-Dinitro-4-phenylthio-benzoic acid A mixture of 4-chloro-3,5-dinitro-benzoic acid (24.6 g.), thiophenol 1 1.3 ml.), sodium hydrogen carbonate g.), and water (200 ml.) is left standing, until the evolution of carbon dioxide has ceased. Then the reaction mixture is heated to 85 C. for 1 hour. The hot solution is thereafter filtered and the filtrate acidified with 4 N hydrochloric acid. After cooling, the precipitate is collected by filtration and recrystallized from aqueous ethanol. The 3,5-dinitro-4-phenylthio-benzoic acid is obtained with a melting point of 197 198 C.

B. 3-Amino-5nitro-4-phenylthio-benzoic acid A solution of 3,5-dinitro-4-phenylthio-benzoid acid (50 g.) in 0.5 N sodium hydrogen carbonate (900 ml.) is cooled to 7 C. and a solution of sodium dithionite (62 g. containing 87% sodium dithionite) in water (500 ml.) is added during 12 minutes, while stirring and keeping the temperature at 71 2 C. After filtration 4 N hydrochloric acid 180 ml.) is added to the still cold filtrate, and after stirring for 8 hours, the crystallized 3-amino-5-nitro-4-phenylthio-benzoic acid is collected and recrystallized from aqueous ethanol. The compound is obtained with a melting point of 215 217 C.

C. Ethyl 3-benzylamino-5-nitro-4-pheny1thio benzoate A mixture of 3-amino-5nitro-4-phenylthio-benzoic acid g.), benzyl bromide (48 g.), and anhydrous ethanol 450 ml.) is refluxed for 6 hours. After cooling, the precipitated ethyl 3-benzylamino-5-nitro-4-phenylthio-benzoate is collected by filtration and recrystallized from ethanol. The compound is obtained with a melting point of 103 105 C.

D. 3-Benzylamino-5-nitro-4-phenylthio-benzoic acid A mixture of ethyl 3-benzylamino-5-nitro-4 phenylthio-benzoate (10 g.), l N sodium hydroxide (150 ml.), and water 150 m1.) is heated on a steam bath for 1 hour. After cooling, 1 N hydrochloric acid (155 ml.) is added, the precipitate collected by filtration and recrystallized from aqueous ethanol. The 3-benzylamino-5-nitro-4 phenylthio-benzoic acid is obtained with a melting point of 175 176.5 C.

E. 5-Amino-3-benzy1amino4-phenylthio-benzoic acid By using 3-benzylamino-5-nitro-4-phenylthiobenzoic acid (6 g.), sodium dithionite (10.8 g.), aqueous ammonia (36 ml.), water (70 ml.), and 4 N hydrochloric acid (100 ml.) and following the procedure of example 1 D, the 5-amino-3-benzylamino-4- phenylthiobenzoic acid is obtained with a melting point of 187 189 C.

EXAMPLE 3 A. n-butyl 3-amino-5-nitro-4-phenoxy-benzoate A mixture of 3-amino-5-nitro-4-phenoxy-benzoic acid (Example 1 A) (12.5 g.), n-butanol (100 ml.) and concentrated sulfuric acid is refluxed for 1.5 hours.

Then 60 ml. of the solvent are distilled off and after cooling and addition of petrol ether (100 ml.) the nbutyl 3-amino-5-nitro-4-phenoxy-benzoate is precipitated. The crude ester is suspended in water (200 ml.) and by addition of l N sodium hydroxide the pH is adjusted to 7, whereby the pure n-butyl 3-amino-5-nitro- 4-phenoxy-benzoate is obtained with m.p. 81 C.

B. 3-n-Butylamino-4-phenoxy-5-nitro-benzoic acid A mixture of n-butyl 3-amino-5-nitro-4-phenoxybenzoate (15 g.), toluene (250 ml.) and di-n-butyl sulfate (48 g.) is heated under gentle reflux for 60 hours.

After cooling the reaction mixture is extracted with 1 N sodium hydrogen carbonate ml.) and water 100 ml.), whereafter the toluene is removed in vacuo. 2 N sodium hydroxide (160 ml.) and ethanol are added to the residue, and the reaction mixture is heated on a steam bath for 2 hours. The ethanol is removed by distillation. After cooling and adjusting the pH to 1.5 the crude acid is extracted with diethyl ether (500 ml.). After evaporation in vacuo the crude 3-n-butylamino- 4-phenoxy-5-nitro-benzoic acid is recrystallize twice from benzene to form the pure compound with m.p.

C. 5-Amino-3-n-butylamino-4-phenoxy-benzoic acid EXAMPLE 4.

A. Ethyl 4benzoyl-3,S-dinitro-benzoate A mixture of 4-carbethoxy-2,6-dinitro-benzoic acid (10.0 g.) and thionyl chloride (50 ml.) is refluxed for 1 hour. The resulting solution is evaporated in vacuo and the remaining 4-carbethoxy-2,6-dinitro-benzoyl chloride is dissolved in dry benzene (100 ml.). Anhydrous aluminum chloride (10 g.) is then added in pottions, while stirring vigorously at room temperature.

After the addition is complete, the mixture is stirred for an additional 18 hours and is then refluxed for 1 hour. The reaction mixture is then poured onto a mixture of ice (about 200 g.) and concentrated hydrochloric acid (25 ml.). The precipitated material is collected by til tration and is then dissolved in methylene chloride (about ml.). This solution is washed with water, dried (MgSO and evaporated in vacuo. The residue is triturated with ethanol (30 ml.), the precipitate filtered off and washed with ethanol followed by petroleum ether. After drying, crude ethyl 4'benzoyl-3,5- dinitro-benzoate is obtained with a melting point of about C. From the benzene layer of the motherliquors a further crop with the same melting point is obtained. Recrystallization twice from methylcellosolve raises the melting point to 172 173 C.

B. 4-Benzoyl-3,S-dinitro-benzoic acid To a hot solution of ethyl 4-benzoyl-3,5-dinitrobenzoate (17 g.) in methylcellosolve (85 ml.), 4 N sodium hydroxide (25 ml.) is added in portions within 5 minutes. The solution is then heated on a steam bath for a further 5 minutes, cooled and acidified with 4 N hydrochloric acid (27.5 ml.). The resulting precipitate is collected by filtration and washed with water. After drying, 4-benzoyl-3,S-dinitro-benzoic acid with a melting point of about 245 C. (dec.) is obtained. Recrystallization from 50% ethanol raises the melting point to 248 251 C. (dec.).

C. 3-Amino-4-benzoyl-5-nitro-benzoic acid A solution of 4-benzoyl-3,S-dinitro-benzoic acid (10.6 g.) in a mixture of pyridine (21.5 ml.) and water (60 ml.) is cooled to 15 C. To the stirred solution, sodium dithionite (14.0 g.) is added in portions over a period of 7 minutes keeping the temperature at 15 17 C. After the addition is complete, the stirring at 15 C. is continued for a further 7 minutes. The resulting red solution is carefully acidified with concentrated hydrochloric acid (40 ml.) keeping the temperature below 20 C. The reaction mixture is left at room temperature for about 20 hours. The precipitated material is then collected by filtration and washed with water. After recrystallization from acetonitrile, 3-amino-4- benzoyl-S-nitro-benzoic acid with a melting point of 203 204 C. (dec.) is obtained.

D. 4-Benzoyl-3-benzylamino-5-nitro-benzoic acid A solution of 3-Amino-4-benzoyl-5-nitro-benzoic acid (3.0 g.) and benzylbromide (3.0 ml.) in methylcellosolve (15 ml.) is heated on a steambath for 7 hours. 4 N sodium hydroxide (15 ml.) is added and the heating is continued for a further 30 min. After cooling, the resulting solution is carefully acidified with 4 N hydrochloric acid (20 ml.). The precipitated oil crystallizes on standing overnight. The material is then triturated with ethanol (25 ml.) and is collected by filtration. After drying and recrystallization from ethanol, 4- benzoyl-3-benzylamino-5-nitro-benzoic acid is obtained with a melting point of 197 199 C. (dec.).

E. -Amino-4-benzoyl-3-benzylamino-benzoic acid To a solution of 4-benzoyl-3-benzylamino-5-nitrobenzoic acid 1.5 g.) in a mixture of pyridine (7.5 ml.) and water (7.5 ml.), sodium dithionite (3.5 g.) is added in portions while stirring at room temperature. After the addition is complete, the reaction mixture is heated on a steambath for 1 hour, and is then evaporated in vacuo. The residue is dissolved in water (about 20 ml.) and the solution is acidified to pH 2,0 with hydrochloric acid. The resulting precipitate is collected by filtration and washed with water. After drying and recrystallization from ethanol, 5-amino-4-benzoyl-3- benzylamino-benzoic acid is obtained with a melting point of about 192 194 C. (dec.).

EXAMPLE 5.

5-Amino-3-benzylamino-4-(a-hydroxybenzyl)benzoic acid To a stirred solution of 5-amino-4-benzoyl 3- benzylaminobenzoic acid (3.5 g.) in methanol (35 ml.), sodium borohydride (1.5 g.) is'added in small portions during 30 minutes. After additional stirring for 3 hours, the solution is carefully acidified with concentrated hydrochloric acid and is then diluted with water to precipitate 5-amino-3-benzylamino-4-(a-hydroxybenzyl)benzoic acid.

EXAMPLE 6. 5-Amino-4-benzyl-3-benzylamino-benzoic acid A mixture of 5 -amino-4-benzoyl-3 benzylaminobenzoic acid (3.5 g.), hydrazine hydrate 6.0 ml.), potassium hydroxide (2.0 g.), water (6.0 ml.) and diethyleneglycol (25 ml.) is stirred at C. for 3 hours. The temperature is then during about 1 hour raised to 215 C. allowing volatile material to distil off. Finally the resulting solution is stirred at 215 220 C. for 3-4 hours until the nitrogen evolution has ceased. After cooling, the solution is diluted with water (25 ml.) and acidified with concentrated hydrochloric acid. The precipitate is collected by filtration, washed with water, dried and recrystallized from ethanol to give 5-amino-4-benzyl-3- benzylamino-benzoic acid with a melting point of 212 213 C. (dec.).

EXAMPLE 7.

A. 4-Chloro-2-fluoro-S-nitro-benzoic acid To a mixture of concentrated sulfuric acid (100 ml.) and nitric acid (6 ml., containing 96% nitric acid) 4-chloro-2-fluoro-benzoic acid (20.9 g.) is added, while stirring. After additional stirring for 2 hours, the reaction mixture is poured into icewater. The precipitate is collected by filtration and washed with water. After recrystallization from aqueous ethanol the 4- chloro-2-fluoro-5-nitro-benzoic acid is obtained with a melting point of 149 153 C.

B. 2-Benzylamino-4-chloro-5-nitro-benzoic acid A mixture of 4-chloro-2-fluoro-5-nitro-benzoic acid (15 g.), benzylamine (27.4 g.), and anhydrous ethanol (250 ml.) is left at room temperature for 24 hours. The precipitated benzylammonium salt is collected by filtration, washed with alcohol and diethyl ether. Then the obtained salt is suspended in water (400 ml.), and the mixture acidified by addition of 4 N hydrochloric acid while stirring. The precipitated 2-benzylamino-4- chloro-S-nitro-benzoic acid is collected by filtration, washed with water and dried. The compound is obtained with a melting point of 234 236 C. under decomposition.

C. 2-Benzylamino-5-nitro-4-phenoxy-benzoic acid A mixture of 2-benzylamino-4-chloro-5-nitrobenzoic acid (10 g.), phenol (42 g.), and sodium phenolate (11.4 g.) is heated in an oil bath at 140 C. for 4 hours while stirring. Then water (500 ml.) is added and excess of phenol removed from the reaction mixture by steam distillation. After cooling, the precipitated sodium salt of Z-benzylamino-5-nitro-4-phenoxybenzoic acid is collected by filtration and washed with water. This sodium salt is then suspended in warm water (200 ml.) and the mixture acidified by addition of 4 N hydrochloric acid, while stirring. The precipitate is filtered off, washed with water and recrystallized from aqueous methanol to yield 2-benzylamino-5- nitro-4-phenoxy-benzoic acid with a melting point of 180 186 C.

D. 5-Amino-2-benzylamino-4-phenoxy-benzoic acid To a mixture of 2-benzylamino 5-nitro-4-phenoxybenzoic acid (5 g.), aqueous ammonia (125 ml. containing 25% ammonia), and water 125 ml. a solution of sodium dithionite 10 g.) in water (50 ml.) is added,

and the reaction mixture is heated to 45 C. for 10 minutes. The resulting solution is allowed to cool to room temperature. Then acetic acid is added until pH of 5.4, and the precipitate is collected by filtration. After recrystallization from aqueous ethanol the -amino-2- benzylamino-4-phenoxy-benzoic acid is obtained with a melting point of 151 154 C. under decomposition.

EXAMPLE 8.

5-Acetamido-4-benzoyl-3-benzylamino-benzoic acid 5-Amino-4-benzoyl-3-benzylamino-benzoie acid (0.5 g.) is dissolved in acetic anhydride (3 ml.). The mixture is left for 30 minutes and the precipitate is collected by filtration, washed with cold acetic anhydride and petroleum ether. After drying and recrystallization from aqueous ethanol, the 5-acetamido-4-benzoyl-3- benzylamino-benzoic acid crystallizing with onequarter mol. of water is obtained with a melting point of 196 198 C.

EXAMPLE 9.

5-Acetamido-3-benzylamino-4-phenoxy-benzoic acid 5-Amino-3-benzylamino-4-phenoxy-benzoic acid (2 g.) is added to acetic anhydride (20 ml.) while stirring. The stirring is continued for an additional 2 hours. Thereafter the precipitate is collected by filtration and recrystallized from ethanol. The 5-acetamido-3- benzylamino-4-phenoxy-benzoic acid is obtained with a melting point of 235 236 C.

EXAMPLE 10.

3-Benzylamino-4-phenoxy-5-propionamido-benzoic acid By substituting in example 9 propionic anhydride for acetic anhydride, 3-benzylamino-4-phenoXy-5- propionamido-benzoic acid is obtained with a melting point of 214 215 C.

EXAMPLE 1 l.

5-Acetamido-3-benzylamino-4-phenylthio-benzoic acid 5-Amino-3-benzylamino-4-pheny1thio-benzoic acid (0.5 g.) is added to acetic anhydride (5 ml.) while stirring. After additional stirring for 3 hours the reaction mixture is diluted with water (50 ml.). After the acetic anhydride is destroyed, the precipitate is collected and recrystallized from aqueous methylcellosolve. The 5- acetamido-3-benzylamino 4-phenylthio-benzoic acid is obtained with a melting point of 256 258 C.

EXAMPLE 1 2.

3-Benzylamino-5-formamido-4-phenoxy-benzoic acid A solution of 5-amino-3-benzylamino-4-phenoxybenzoic acid (1 g.) in formic acid ml.) is left at room temperature for 2 hours. After evaporation in vacuo, the residue is washed with diethyl ether and recrystallized from ethanol to yield 3-benzylamino-5- formamido-4-phenoxy-benzoic acid with a melting point of 224 226 C.

EXAMPLE l3.

3-Benzylamino-5-formamido-4-phenylthio-benzoic acid A solution of 5-amino-3-benzylamino-4-phenylthiobenzoic acid (0.56 g.) in formic acid (5.6 ml.) is left for 2 hours at room temperature followed by standing for 16 hours in a refrigerator. The precipitation is completed by addition of water ml.). After collection by filtration and recrystallization from aqueous methanol, the 3-benzylamino-5-formamido-4-phenylthiobenzoic acid is obtained with a melting point of 2155 217 C.

EXAMPLE l4.

2-Benzylamino-S-formamido-4-phenoxy-benzoic acid A solution of 5-amino-2-benzylamino-4-phenoxy-- benzoic acid (1 g.) in formic acid (10 ml.) is left for 24 hours. The reaction mixture is then poured into water ml.). The precipitate is collected by filtration, washed with water and recrystallized from methanol/- water to yield Z-benzylamino-5-formamido-4-phenoxybenzoic acid with a melting point of 218 C. under decomposition.

EXAMPLE 1 5.

5-Acetamido-Z-benzylamino-4-phenoxy-benzoic acid A mixture of S-amino-2-benzylamino-4-phenoxybenzoic acid (1 g.), acetic anhydride (0.3 ml.), and acetic acid (10 ml.) is stirred for l and one-half hours. Water (100 ml.) is then added and the pricipitate collected by filtration and washed with water. After recrystallization from methanol/water, the S-acetamido- 2-benzylamino-4-phenoxy-benzoic acid is obtained with a melting point of 209 214 C. under decomposition.

EXAMPLE l6.

3-Benzylamino-4-phenoxy-5 n-propylureylone-benzoic acid A mixture of 5-amino-3-benzylamino-4-phenoxybenzoic acid (1.67 g.), n-propyl isocyanate (0.425 g.), and acetone (25 m1.) is left for 18 hours at room temperature. After cooling, the precipitate is collected by filtration and recrystallized from acetone/petroleum ether. The 3-benzylamino-4'phenoxy-5-npropylureylene-benzoic acid is obtained with a melting point of 210 211 C.

EXAMPLE 17.

3-Benzylamino-4-phenoxy-S-ureido-benzoic acid A mixture of 5-amino-3-benzylamino-4-phenoxybenzoic acid (3.35 g.), potassium cyanate (l g.), and acetic acid (50 ml.) is left at room temperature for 5 hours. Water (250 ml.) is added, the precipitate collected by filtration and redissolved in boiling l N sodium hydrogen carbonate (15 ml.). After cooling, the precipitated sodium salt of 3-benzylamino-4phenoxy- S-ureido-benzoic acid is collected and washed with water. The sodium salt is then dissolved in boiling water (80 ml.), 1 N hydrochloric acid (5 ml.) is added, and. after cooling, the precipitated 3-benzylamino-4- phenoxy-S-ureido-benzoic acid collected by filtration. After recrystallization from ethanol the compound is obtained with a melting point of 213 214 C.

EXAMPLE 1 8.

2-Benzylamino-4-phenoxy-5-ureido-benzoic acid To a mixture of 5-amino-2-benzylamino-4-phenoxybenzoic acid (1 g.), acetic acid (15 ml.), and water (4 ml.) potassium cyanate (0.3 g.) is added in small portions during 8 minutes, whereafter the reaction mixture is stirred for a further 10 minutes. Water (50 ml.) is then added while stirring, and the precipitate collected by filtration and washed with water. After recrystallization from methanol the 2-benzylamino-4-phenoxy-5- ureido-benzoic acid is obtained with a melting point of 214 215 C. under decomposition.

EXAMPLE 1 9.

2-Benzylamino-5-carbethoxyamino-4-phenoxybenzoic acid To an ice cooled mixture of -amino-2-benzylamino- 4-phenoxy-benzoic acid (1 g.), triethylamine (0.6 g.), and water (35 ml.), ethyl chloroformate (0.25 ml.) is added while stirring. The stirring is continued for 1 /2 hours at 2 5 C. and 30 minutes at room temperature. After acidification with hydrochloric acid the precipitate is collected by filtration and washed with water. After recrystallization from methanol/water the 2- benzylamino-S-carbethoxyamino-4-phenoxy-benzoic acid is obtained with a melting point of 192 194 C. under decomposition.

EXAMPLE 20.

3 -Benzylamino-5-carbethoxyamino-4-phenoxybenzoic acid 1 To a mixture of 5-amino-3-benzylamino-4-phenoxybenzoic acid (1.4 g.), acetone (50 ml.), and water (50 ml.), 2 N sodium hydroxide is added until a pH of 7.5. Then a solution of ethyl chloroformate (0.65 g.) in acetone ml.) is added during 30 minutes to the reaction mixture while keeping the temperature at 5 10 C. and the pH at 7.5 using an automatical end point titrator. When the base consumption has becomenegligible, 4 N hydrochloric acid is added until a pH of 2.5. The precipitate is collected by filtration and recrystallized from ethanol to yield 3-benzylamino-5- carbethoxy-4-phenoxy-benzoic acid with a melting point of 215 C. under destruction.

EXAMPLE 2] 3-n-Butylamino-4-phenoxy-5-ureido-benzoic acid A mixture of 5-amino-3-n-butylamino-4-phenoxybenzoic acid (0.4 g.), acetic acid ml.), and potassium cyanate (0.3 g.) is left at room temperature for 3 hours. Water (50 ml.) is added and the precipitated 3- n-butylamino-4-phenoxy-S-ureido-benzoic acid collected by filtration. After recrystallization from ethanol the compound is obtained with a melting point of 202 204 C.

EXAMPLE 22.

3-Benzylamino-5-methylureylene-4-phenoxy-benzoic acid A solution of methyl isocyanate (0.09 g.) in acetone (5 ml.) is added dropwise to a solution of 5-amino-3- benzylamino-4-phenoxy-benzoic acid (0.67 g.) in acetone (10 ml.) at 5 C. Then the reaction mixture is allowed to reach room temperature and kept at this temperature for 22 hours. After cooling the precipitated 3,-benzylamino-5-methylureylene-4-phenoxy-benzoic acid is collected by filtration and recrystallized from ethanol. The compound is obtained with a melting point of 224 225 C.

EXAMPLE 23.

5-Acetamino-3-benzylamino-4-( ix-hydroxybenzyl) benzoic acid By substituting in example 8,5-amino-3- benzylamino-4( a-hydroxybenzyDbenzoic acid for the 5-amino-4-benzoyl-3-benzylaminobenzoic acid, 5- acetamino-3-benzylamino-4-(a-hydroxybenzyl)benzoic acid is obtained with a melting point of 180 18 1 C. (dec.

EXAMPLE 24 4-Benzyl-3-benzylamino-5-ureido-benzoic acid o I R -ii-HN cooH in which R is selected from the group consisting of alkyl derivatives with from 3 to 8 carbon atoms in the carbon chain; and phenyl substituted methyl and ethyl; A is phenylthio; R is selected from the group consisting of hydrogen and lower alkyl groups; and pharmaceutically acceptable salts of the carboxylic acid of formula I.

2. 5-Acetamido-3-benzylamino-4-phenylthiobenzoic acid, and pharmaceutically acceptable salts of the carboxylic acid thereof.

53 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3: 905, l l-6 D d September 2, 1975 Inventor(s) Peter Werner Feit and Ole Bent Tvaermose Nielsen It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the title page the priority document should be listed as follows: British application Serial No. 297 rO/70, filed June 18, 1970.

Signed and Scaled this ninth Day, of December 1975 '[SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Patents and Trademarks 

1. A COMPOUND OF THE FORMULA 1
 2. 5-Acetamido-3-benzylamino-4-phenylthio-benzoic acid, and pharmaceutically acceptable salts of the carboxylic acid thereof. 